Data for: Projecting changes in the frequency and magnitude of ozone pollution events under uncertain climate sensitivity

Climate change is projected to worsen ozone pollution over many populated
regions, with larger impacts at higher concentrations. More intense and
frequent ozone episodes risk setbacks to human health and environmental
policy achievements. However, assessing these changes is complicated by
uncertain climate sensitivity, closely related to climate model response,
and internal variability in simulations projecting climate’s influence on
air quality. Here, leveraging a global modeling framework that one-way
couples a human activity model, an Earth system model of intermediate
complexity, and an atmospheric chemistry model, we investigate the role of
climate sensitivity in climate-induced changes to high ozone pollution
episodes in the United States using multiple greenhouse gas emissions
scenarios, representations of climate sensitivity, and initial condition
members. We bias correct and evaluate historical model simulations,
identifying modeled and observed O3 episodes using extreme value theory,
and extend the approach to projections of mid- and end-century climate
impacts. Results show that the influence of climate sensitivity can be as
significant as that of greenhouse gas emissions scenario absent precursor
emissions changes. Climate change is projected to increase the magnitude
of the highest annually occurring O3 concentrations by over 2.3 ppb on
average across the U.S. at mid-century under a high climate sensitivity
and moderate emissions scenario, but the increase is limited to less than
0.3 ppb under lower climate sensitivity. Further, we show that areas in
the U.S. currently meeting air quality standards risk being pushed into
non-compliance due to a climate-induced increase in frequency of high
ozone days.